Blends of fluoroplastics and fluoroelastomers

Abstract

A composition and method for preparing it is disclosed. The composition in a blend of a cured fluoroelastomer which except for the cure sites is a perfluorocarbon and a thermoplastic copolymer of tetrafluoroethylene which is present as generally spherical particles having a particle size of less than 10 microns. The composition is prepared by blending the fluoroelastomer and thermoplastic copolymer at a temperature above the melting point of the thermoplastic copolymer followed by curing the fluoroelastomer.

We claim: 
     
       1. A melt blended composition comprising (A) 100 parts by weight of a cured fluoroelastomer consisting essentially of from 79.9 to 52 mole % units derived from tetrafluoroethylene, 20 to 45 mole % units derived from a perfluoroalkylvinyl ether wherein the alkyl group contains from 1 to 10 carbon atoms, and 0.1 to 4.0 mole % cure site monomer units derived from vinyldiene fluoride, trifluoroethylene, vinyl fluoride, CH 2  ═CHR f  where R f  is a perfluoroalkyl group containing from 1 to 5 carbon atoms, perfluorophenoxy substituted perfluoroalkylene vinyl ethers wherein the perfluoroalkylene group contains from 1 to 5 carbon atoms, N═C(R' f  --O) n  CF═CF 2  where R' f  is a perfluoroalkylene group of 2 or 3 carbon atoms and n is 1-4, fluoroolefins of 2 to 5 carbon atoms containing 1 or 2 bromo substitutents or fluoroolefins of 2 to 5 carbon atoms, containing 1 or 2 iodo substituents, (B) and from 2 to 50 parts by weight of a thermoplastic perfluorocarbon copolymer containing at least 50 mole % units derived from tetrafluoroethylene having a melting point above 300° C. which is present as generally spherical particles having a particle size of less then about 10 microns, said composition being melt blended at a temperature which is sufficiently high to melt the thermoplastic tetrafluoroethylene copolymer. 
     
     
       2. A process of preparing a blend of (A) 100 parts of fluoroelastomer consisting essentially of from 79.9 to 52 mole % units derived from tetrafluoroethylene, 20 to 45 mole % units derived from a perfluoroalkylvinyl ether wherein the alkyl group contains from 1 to 10 carbon atoms, and 0.1 to 4.0 mold % cure site monomer units derived from a vinylidene fluoride, trifluoroethylene, vinyl fluoride, CH 2  ═CHR f  where R f  is a perfluoroalkyl group containing from 1 to 5 carbon atoms, perfluorophenoxy substituted perfluoroalkylene vinyl ethers wherein the perfluoroalkylene group contains from 1 to 5 carbon atoms, N═C(R' f  --O) n  CF═CF 2  where R' f  is a perfluoroalkylene group of 2 or 3 carbon atoms and n is 1-4, fluoroolefins of 2 to 5 carbon atoms containing 1 or 2 bromo substituents or fluoroolefins of 2 to 5 carbon atoms containing 1 or 2 iodo substituents, and (B) from 2 to 50 parts by weight of a thermoplastic copolymer containing at least 50 mole % units derived from tetrafluoroethylene comprising blending said fluoroelastomer and thermoplastic copolymer at a temperature above the melting point of the thermoplastic copolymer followed by addition of curing ingredients at below 100° C. and curing the fluoroelastomer. 
     
     
       3. The composition of claim 1 wherein the thermoplastic perfluorocarbon contains 50 to 98 mole % units derived from tetrafluoroethylene and 2 to 50 mole % units derived from hexafluoropropylene or a perfluoroalkylvinyl ether wherein the perfluoroalkyl group contains from 1 to 10 carbon atoms. 
     
     
       4. The composition of claim 3 wherein the fluoroelastomer contains from 74.8 to 57 mole % units derived from tetrafluoroethylene, 25 to 40 mole % units derived from perfluoroalkylvinyl ether and 0.2 to 3.0 mole % cure site monomer derived units. 
     
     
       5. The composition of claim 4 wherein the thermoplastic perfluorocarbon contains from 97 to 75 mole % units derived from tetrafluoroethylene and 3 to 25 mole % units derived from hexafluoropropylene or perfluoroalkylvinyl ether. 
     
     
       6. The composition of claim 5 wherein there is present from 5 to 30 parts by weight thermoplastic perfluorocarbon copolymer per 100 parts by weight fluoroelastomer. 
     
     
       7. The composition of claim 1 wherein a curing agent is present adapted to cure the cure site monomer units present. 
     
     
       8. The composition of claim 7 wherein the fluoroelastomer contains 79.9 to 52 mole % units derived from tetrafluoroethylene, 20 to 45 mole % units derived from perfluoroalkylvinyl ether wherein the alkyl group contains from 1 to 10 carbon atoms, and 0.1 to 4.0 mole % of units derived from a cure site monomer. 
     
     
       9. The composition of claim 8 wherein the thermoplastic perfluorocarbon contains 50 to 98 mole % units derived from tetrafluoroethylene and 2 to 50 mole % units derived from hexafluoropropylene or a perfluoroalkylvinyl ether wherein the alkyl group contains from 1 to 10 carbon atoms. r 
     
     
       10. The composition of claim 9 wherein the cure site monomer units are derived from vinylidene fluoride, trifluoroethylene, vinyl fluoride, ethylene, CH 2  ═CHR f  wherein R f  is a perfluoroalkyl group containing 1 to 5 carbon atoms, perfluorophenoxy substituted perfluoroalkylene vinyl ethers wherein the perfluoroalkylene group contains from 1 to 5 carbon atoms, N C(R' f  --O) n  CF═CF 2  where R' f  is a perfluoroalkylene group of 2 or 3 carbon atoms and n is 1-4, fluoroolefins of 2 to 5 carbon atoms containing 1 or 2 bromo substituents or fluoroolefins of 2 to 5 carbons atoms containing 1 or 2 iodo substituents. 
     
     
       11. The composition of claim 10 wherein the fluoroelastomer contains from 74.8 to 57 mole % units derived from tetrafluoroethylene, 25 to 40 mole % units derived from perfluoroalkylvinyl ether and 0.2 to 3.0 mole % cure site monomer derived units. 
     
     
       12. The composition of claim 11 wherein the thermoplastic perfluorocarbon contains from 97 to 75 mole % units derived from tetrafluoroethylene and 3 to 25 mole % units derived from hexafluoropropylene or perfluoroalkylvinyl ether. 
     
     
       13. The composition of claim 12 wherein there is present 5 to 30 weight percent thermoplastic perfluorocarbon per 100 parts fluoroelastomer. 
     
     
       14. The process of claim 2 wherein the thermoplastic perfluorocarbon contains 50 to 98 mole % units derived from tetrafluoroethylene and 2 to 50 mole % units derived from hexafluoropropylene or a perfluoroalkylvinyl ether wherein the alkyl group contains from 1 to 10 carbon atoms. 
     
     
       15. The process of claim 14 wherein the fluoroelastomer contains from 74.8 to 57 mole % units derived from tetrafluoroethylene, 25 to 40 mole % units derived from perfluoroalkylvinyl ether and 0.2 to 3.0 mole % cure site monomer derived units. 
     
     
       16. The process of claim 15 wherein the thermoplastic perfluorocarbon contains from 97 to 75 mole % units derived from tetrafluoroethylene and 3 to 25 mole % units derived from hexafluoropropylene or perfluoroalkylvinyl ether. 
     
     
       17. The process of claim 16 wherein there is present from 5 to 30 parts by weight thermoplastic perfluorocarbon copolymer per 100 parts by weight fluoroelastomer.